“Microfluidics” generally refers to systems, devices, and methods for processing small volumes of fluids. Because microfluidic systems can process a wide variety of fluids, such as chemical or biological samples, these systems have many application areas, such as biochemical assays (for, e.g., medical diagnoses), biochemical sensors, or life science research in general.
One type of microfluidic device is a microfluidic chip. Microfluidic chips may include micro-scale features (or “microfeatures”), such as channels, valves, pumps, and/or reservoirs for storing fluids, for routing fluids to and from various locations on the chip, and/or for reacting fluidic reagents. In some cases, microfluidic chips may include more complex micro-scale structures such as mixing devices or sensors for performing other processing functions on the fluids. A microfluidic chip that integrates various microfeatures to provide various fluid processing functions is sometimes called a “Lab-on-a-chip.”
However, many existing microfluidic devices are prohibitively expensive or prohibitively difficult to operate to be suitable for many applications. For example, many existing systems are too expensive to be disposable or do not have enough programmed automation to be operated by an untrained field technician. Therefore, these systems cannot be used in certain non-laboratory environments. Moreover, many microfluidic systems are built for one specific application, and cannot be adapted or customized for other applications. Many microfluidic systems are not modular, and therefore cannot benefit from the efficiencies of mass-production or allow a user to reconfigure easily the system for various applications at hand.
Moreover, existing microfluidic systems lack adequate detection and analysis systems. While microfluidic devices deliver higher process speeds and require only small volumes of sample, these small volumes of samples are difficult to detect and analyze. By way of comparison, an exemplary non-microfluidic implementation is an Enzyme Linked Immunosorbent Assay (ELISA), using a 96 well microplate with a well diameter of 6 mm for the sample cuvet. In this case, the final volume for a spectrometer measurement is around 100 .mu.l and corresponds to an optical path length for an optical detector of about 4 mm. In contrast, a typical microfluidic channel or reservoir may have a channel depth of less than about 100 microns. This optical path length is thus about 40-fold lower than for a conventional microplate assay, which can correspond to a 40-fold decrease in detection signal intensity.
Furthermore, many existing detection systems do not adequately integrate to a microfluidic chip. As a result, an untrained technician may have difficulty interfacing the microfluidic chip to the detector in order to provide meaningful results. Finally, many existing systems use expensive optical components.
Thus, there exists a need for improved microfluidic systems for processing fluids, such as biological or chemical samples. It is desired that the systems are inexpensive and preferably disposable. It is desired that the systems be simple to operate and that many or substantially all of the fluid processing steps be automated. It is desired that the systems be customizable, and be modular such that the system can be easily and rapidly reconfigured to suit various applications. It is desired that the systems include integrated detection systems which provide high detection sensitivity, but are inexpensive and preferably disposable.